Hibernate Framework Hibernate Performance Tuning 2

Question 1

What does session.clear() do in Hibernate?

Accepted Answer

Clears the first-level cache, detaching all managed entities

Answer

session.clear() removes all entities from the Session's first-level cache, releasing their memory without closing the session.

Question 2

Why should session.clear() be called periodically during bulk inserts?

Accepted Answer

To prevent OutOfMemoryError by releasing accumulated entities from the first-level cache

Answer

During bulk operations, the first-level cache accumulates all processed entities in memory; periodically calling clear() prevents heap exhaustion.

Question 3

What does the 'hibernate.order_inserts=true' property do?

Accepted Answer

Groups INSERT statements by entity type to improve JDBC batch efficiency

Answer

Ordering inserts by entity type allows Hibernate to batch together INSERT statements for the same table, maximizing JDBC batch efficiency.

Question 4

What query hint can be used to force Hibernate to use a specific database index?

Accepted Answer

query.addQueryHint("indexName")

Answer

The addQueryHint() method passes a native database index hint to the generated SQL, guiding the query planner to use a specific index.

Question 5

What is a projection query in Hibernate and why is it more efficient?

Accepted Answer

A query that selects specific fields instead of full entities, reducing data transfer

Answer

Projection queries select only the columns needed rather than loading full entity objects, reducing memory usage and data transfer from the database.

Hibernate Framework Practice Test